The problems posed by substances which deplete the atmospheric ozone layer were addressed in Montreal, where the protocol imposing a reduction in the production and use of chlorofluorocarbons (CFCs) was signed. This protocol has been the subject of amendments which have required the abandoning of CFCs and have extended regulation to other products, including hydrochlorofluorocarbons (HCFCs).
The refrigeration and air conditioning industries have invested a great deal in the replacement of these refrigerants and it is because of this that hydrofluorocarbons (HFCs) have been marketed.
In the motor vehicle industry, the air conditioning systems of vehicles sold in many countries have been changed from a refrigerant comprising chlorofluorocarbon (CFC-12) to that of hydrofluorocarbon (1,1,1,2-tetrafluoroethane: HFC-134a), which is less harmful to the ozone layer. However, from the viewpoint of the objectives set by the Kyoto protocol, HFC-134a (GWP=1430) is regarded as having a high heating power. The contribution to the greenhouse effect of a refrigerant is quantified by a criterion, the GWP (Global Warming Potential), which summarizes the heating power by taking a reference value of 1 for carbon dioxide.
Hydrofluoroolefins (HFOs) have a low heating power and therefore meet the objectives set by the Kyoto protocol. Document JP 4-110388 discloses hydrofluoropropenes as heat transfer agents.
In the industrial sector, the refrigerating machines most commonly used are based on cooling by evaporation of a liquid refrigerant. After vaporization, the refrigerant is compressed and then cooled in order to return to the liquid state and thus continue the cycle.
The refrigerant compressors used are of reciprocating, centrifugal, scroll or screw type. In general, internal lubrication of compressors is essential in order to reduce wear and heating of the moving parts, to render them completely leak-tight and to protect them from corrosion.
In addition to having good properties as a heat transfer agent, in order for a refrigerant to be accepted commercially, it must in particular be thermally stable and be compatible with lubricants. This is because it is highly desirable for the refrigerant to be compatible with the lubricant used in the compressor, present in the majority of refrigeration systems. This refrigerant and lubricant combination is important for the use and the effectiveness of the refrigeration system; in particular, the lubricant must be sufficiently soluble or miscible in the refrigerant throughout the operating temperature range.
Thus, polyalkylene glycols (PAGs) have been developed as lubricants of HFC-134a in motor vehicle air conditioning.
Tests for compatibility of 1,1,3,3,3-pentafluoropropene, of 1,3,3,3-tetrafluoropropene and of 3,3,3-trifluoropropene with PAGs have been described in example 3 of document WO 2004/037913. This document is content with giving only the visual appearance of the samples after the tests.